1. Field of the Invention
The present invention relates to three-dimensional printing apparatuses.
2. Description of the Related Art
A three-dimensional printing apparatus is conventionally known in which a liquid photo-curable resin stored inside a tank is irradiated with light so as to cure the photo-curable resin, thus forming a three-dimensional object (see, for example, JP 2003-39564 A).
A three-dimensional printing apparatus of this type includes a base provided with an opening, a tank placed on the base, and a raisable and lowerable holder disposed above the tank. An optical system is disposed below the tank. For example, the optical system includes a light source that emits light and a mirror. The light emitted from the light source is reflected by the mirror. The photo-curable resin inside the tank is irradiated with the reflected light through the opening of the base. A portion of the photo-curable resin inside the tank which has been irradiated with the light is cured. By controlling a light irradiation position, a position at which the resin is to be cured is appropriately changed. Hence, the cured resin can form a desired cross-sectional shape. A desired cross-sectional shape is continuously formed downward by sequentially raising the holder. As a result, a desired three-dimensional object is formed by the cured photo-curable resin.
In performing printing of a three-dimensional object (hereinafter simply referred to as “three-dimensional printing”), a cover that covers the tank and the holder is disposed above the base so as to prevent leakage of light to outside. In the three-dimensional printing apparatus disclosed in JP 2003-39564, the tank (which is referred to as a “trough” in JP 2003-39564) is reduced in area in a plan view, and therefore, the cover is reduced in size. As a result, the apparatus is reduced in size.
In the above-described three-dimensional printing apparatus, an object is formed layer by layer by sequentially raising the holder. When the holder is raised, it is important to rapidly and stably supply a liquid photo-curable resin, which is to form a next layer, to a region under a cured photo-curable resin lifted by the holder. In the three-dimensional printing apparatus disclosed in JP 2003-39564, the tank is only slightly larger than the holder (which is referred to as a “carrier platform” in JP 2003-39564) in the plan view. Hence, the area of the tank in the plan view is small. Thus, in this case, it is more difficult for a liquid photo-curable resin to flow inside the tank than when the area of the tank in the plan view is large. Therefore, when the holder is raised, a liquid photo-curable resin that has already slightly been irradiated with light and has thus been somewhat degraded is likely to remain in a region under a cured photo-curable resin. Thus, it is difficult to supply a fresh photo-curable resin that is not yet irradiated with light. Consequently, a resulting three-dimensional object might be degraded in quality, thus making it difficult to form the three-dimensional object as desired.